The present invention relates generally to systems and methods for de-icing aircraft, and more particularly to a system utilizing high speed air for the forced air mechanical removal of snow and ice from the surface of an aircraft.
Prior art de-icing systems and methods have typically consisted of spraying large quantities of de-icing fluids onto snow and ice-covered aircraft surfaces. Though effective, prior art methods normally use environmentally hazardous fluids and therefore require expensive associated systems for fluid storage, usage, collection, recycling, and disposal. Certain prior systems utilize a high-speed air jet blast (alone or in combination with various de-icing fluids) to mechanically dislodge snow and ice, rather than melting it with fluids by chemical or thermal means, and exhibit the advantage of greatly reducing the amounts of fluids required.
U.S. Pat. No. 2,422,746 to Patterson describes a high-pressure air and liquid jet positioned at the forward portion of an airplane wing, so that the jet and the fluid ejected underlie any film of ice that forms on the wing edges and surfaces, tear off accumulations of ice and snow on the forward edges of the wing, and allow the air stream over the wing to tear off the remaining ice accumulated on the rear and upper surfaces of the wing. This system is inappropriate for de-icing aircraft prior to takeoff, and adds to the expense, complexity, weight, and fuel usage in modern aircraft.
U.S. Pat. No. 5,244,168 to Williams describes forced air de-icing using air entrained de-icing fluid (Type I and Type II), a source of compressed air and a mixing nozzle coupled to the source fluid and compressed air which produces the jet air blast, with various fluid spray patterns. The primary parameter for the air jet blast effectiveness is described as momentum per unit mass (air jet velocity). The Williams method sweeps an aircraft surface with an air jet blast alone to remove as much snow and ice as possible and uses the entrained fluid to complete the removal process. Williams uses a conventional turbine auxiliary power unit (APU) as the compressed air source, capable of heated (.about.400.degree. F.) or unheated output, with controlled temperature, pressure and flow rate. An air conduit of unspecified design delivers compressed air to a mixing nozzle depicted in the figures as a straight-sided converging (conical) configuration. The air conduit is configured to enhance heat transfer to an adjacent fluid conduit as a means of heating the fluid. Compressed air is delivered to the mixing nozzle at flow rates of 50-200 mph. Working distance to the aircraft is stated to be up to ten feet. Air jet blasts of 100-200 mph are described as sufficient to mechanically dislodge snow and ice off a wing previously prepared with Type II anti-icing fluid, which is consistent with the operational characteristics of Type II fluid having ice shearing capabilities at aircraft take-off speeds in the same range. A prototype mobile vehicle constructed by Williams includes a Trump de-icing truck with a Garrett APU installed in the rear. High pressure hose of the type used for aircraft engine air starter systems is used in the air conduit along with aluminum pipe of three-inch diameter. The prototype aluminum nozzle is flared with a narrow slot opening. The entire teachings of the Williams patent are incorporated by reference herein.
U.S. Pat. No. 5,755,404 to Numbers describes a system for forced air de-icing of aircraft that includes a source of pressurized air and an axi-symmetric, high momentum focused air jet nozzle having an inlet of diameter D and an outlet of diameter d with an axisymmetric contour defined by a converging portion of first radius near the inlet and a reflex portion of second radius near the outlet, the converging and reflex portions being connected by a convergent conical portion tangent to both the converging and reflex portions, wherein the angle of convergence is equal to or less than 30.degree., D is equal to or greater than 2d, the first radius is equal to or greater than D, the second radius is equal to or greater than d, and the nozzle length is equal to or greater than 1.5 D. The entire teachings of the Numbers patent are incorporated by reference herein.
In a related conventional system, Landoll Corporation supplies for its Model TM-1800 Deicer/Washer truck a modification kit including a bracket for mounting a standard MA-1A turbine APU to the rotating boom of the truck using a trombone air tube assembly on the boom via a braided high-pressure hose and aluminum 90.degree. elbow fixtures, and a generally conically shaped nozzle. This system uses a jet air blast for mechanically dislodging snow and ice.
The prior art systems suffer from one or more disadvantages as a result of the operational inefficiency of the placement of the compressed air source distant from the high speed air delivery nozzle, the consequence of which is that high velocity air flow through the delivery conduit, along with the flow of any de-icer fluid that may be inserted into the air flow for facilitating snow and ice removal from the surface of an aircraft, is subjected to an excessively tortuous path which promotes excessive pressure loss in the flow and substantially decreases efficiency of the compressed air source and of the snow and ice removal process.
The invention solves or substantially reduces in critical importance problems with prior art de-icing systems as just suggested by providing a forced air de-icing system having a compressed air source disposed near the delivery nozzle of the forced air delivery system, preferably near, below or within the operator platform containing the controls, for selectively directing the high speed air flow onto the surface of an aircraft. The invention provides the advantages over prior art systems including higher efficiency of operation, lower equipment cost, lower maintenance costs, improved operator directional control of high speed air at the point of application on the surface of an aircraft, increased efficiency of snow and ice removal from the aircraft, and lower system operating costs.
The invention also provides a fast, economical means of removing snow, ice and sleet, and other frozen deposits from pavements, aircraft ground support equipment, cargo containers, vehicles and other surfaces. Additionally, the invention provides for small quantities of water and/or liquid cleaning agents to be injected into the air stream either upstream or downstream of the nozzle. This high velocity air stream-liquid combination can aggressively wash or decontaminate an aircraft, ground support equipment, cargo containers, vehicles, pavements and other surfaces. This invention offers an advantage over prior art systems that require large quantities of water, de-icing fluid, and soap and which were substantially labor intensive. For both de-icing and cleaning, a liquid jet may be positioned such that the liquid stream enters the high speed air stream downstream of the air nozzle. These flows combine to form a powerful force for cleaning or de-icing a surface.
The functional components including the air compressor, power supply and transmission which connects the power supply to the air compressor are described, and the configurations of the components as installed on a vehicle are identified which provide optimized system integration in terms of operational efficiency and cost of ownership. Because the conventional forced air de-icing systems are manually controlled, ineffective and inefficient operation of the de-icer system may result from operator error. The invention suggests methods for automated system control to avoid problems associated with operator control.
As used herein, the term "de-icing" is intended to define and include the removing of snow, ice, freezing rain, sleet, frost, and other materials normally understood to be the objects of aircraft de-icing procedures.
It is therefore a principal object of the invention to provide an improved aircraft de-icing system and method.
It is a further object of the invention to provide an aircraft de-icing system and method using forced air.
It is another object of the invention to provide an aircraft de-icing system and method wherein the forced air is delivered with increased efficiency.
It is yet another object of the invention to provide an aircraft de-icing system and method having the high speed air source disposed near the delivery nozzle and operator platform of the delivery system.
It is another object of the invention to provide an aircraft de-icing system wherein the length of the conduit required to connect the high speed air source to the delivery nozzle is minimized.
It is yet another object of the invention to provide a forced air aircraft de-icing system wherein the source of high speed air and the delivery nozzle connected thereto are structured separately from the supporting delivery vehicle and aerial boom.
It is another object of the invention to provide a forced air aircraft de-icing system wherein the airflow pressure and airflow energy losses between the source of high speed air and the deliver nozzle are minimized.
It is yet another object of the invention to provide a forced air aircraft de-icing system wherein the position of the delivery nozzle is substantially remotely controllable.
It is another object of the invention to provide a forced air aircraft de-icing system of minimum physical size, and which is characterized by substantial ease of installation on and removal from a supporting vehicle.
These and other objects of the invention will become apparent as the detailed description of representative embodiments proceeds.